Jam detection

Hi,
I see in the wiki that there's support for simple switch based filament-out detection, but not mousewheel style. I'd like to see support for the mousewheel style, not just for filament out, but for tracking that filament is actually moving when it's supposed to be, allowing automatic pausing or aborting of the print, e.g. in the case of the extruder grinding up the filament or similar.

This wouldn't need to be any kind of accurate reporting of exact length of filament, vs expected, just a vague "yes, there's still some movement from the filament" or "nope, it's not moved in a while".

I've been trying different extruders of late, and have had a lot of air-printing due to over-tightened, or over powered extruders - so all my fault and expected (experiments can fail, who'd've thunk it?), but it did occur to me while trying to tune these things in, that this feature would be a handy one.